1. Field of the Invention
The present invention relates to a method for investigating a ground structure of a paved road such as an asphalt-paved road in which the ground structure under the pavement can be visually analyzed.
2. Description of the Related Art
The ground structure of a paved road is composed of a roadbed A and a paved floor B on the roadbed A as shown in FIG. 5, and the roadbed A comprises, for example, a sand layer 2 rammed down on a miscellaneous soil layer 1 which is mixed with ballasts and crushed matters, and the paved floor B is composed of, for example, three asphalt layers 3, 4 and 5 in which the size of a mixed gravel is decreased in order from the gravel included in the bottom asphalt layer 3 which is located on the sand layer 2 to the gravel in the uppermost layer 5 which forms the road surface.
As for the road thus constructed, generally the design documents are reserved and used for such purposes as a repair work of the pavement.
However, the design documents of the pavements are not always specified so as to be permanently reserved so that sometimes they are lost, or some of the pavements are found to be changed from the original structure due to such cases as a later improvement or reconstruction work and the construction records of these later works are not always transferred to successors.
Meanwhile, even in a normal case, the design documents of the road and the present structure of the road do not always correctly agree with each other.
Therefore, when the pavement structure of a place selected as an object of repair is actually not clear, usually the pavement structure is investigated in advance, and then a design for the repair of the road is prepared according to the results of the investigation.
In the investigation of the ground structure of a pavement, at first a preparatory investigation is conducted to specify the location where repair is needed next, the ground of the place to be repaired and specified by the preparatory investigation is investigated.
In the ground investigation work, there is a trial digging method in which the investigation area is divided into such as a few meters square, for example, 1 m .times.2 m area and the paved floor of the area is cut by an engine cutter and then the ground of the area is dug up by such as a power shovel to investigate. However in this trial digging method there are many problems such as that large scale machines have to be prepared, repair work is needed after the investigation, and also many times the working area occupies, for example, one traffic lane in one side of the road causing retard of traveling vehicles, and further it takes a long time to complete the work.
Therefore, a boring method which investigates the ground structure of a place to be investigated by means of boring is now in use.
In this boring method, it is so arranged that a hole which has a diameter of several tens of centimeters, for example, a large hole with a diameter of 36 cm, or a medium size hole with a diameter of 20 cm is bored vertically from the surface of the road and a gathered core is visually investigated.
In the ground investigation of the conventional boring method, a vertical structure of the ground of a road is visually investigated according to a core filled in a mold gathering attachment such as a pipe. However, many of the ground areas needing to be investigated are usually sunk to a roadbed A being affected by a leaked water from such as service water and/or drainage.
Therefore, in the core in the mold gathering attachment, the sunk portion of the ground is not gathered as it is a vacant space, while the total portion is gathered in a compacted state so that there is a problem that the gathered core do as not agree with the actual vertical ground structure.
Also, there is another problem that, even if damages such as cracks are generated in respective layers 3, 4 and 5 of the asphalt-paved floor B, those cracks are gathered in a crushed and filled state due to the pressure accompanying the gathering of the core, so that those cracks can not be detected.
Further, the hole made by boring has a diameter of a large size or a medium size and also has a depth of from approximately 1 through 2 m. Therefore a large amount of cement is needed for filling up the hole after finishing the investigation, and incidentally workings of the cement such as kneading and some workers therefor are required, thereby the labor time is increased, and as it is difficult to repair it perfectly, this has been a cause of deterioration to the pavement.